There are many types of emergency locking safety belt retractors for use in vehicles, and they generally can be divided into major classifications depending on how they lock. One type locks automatically by a slight retraction of the belt, and is maintained in the locking position at all times during use of the safety belt. The other two types are adapted to be normally unlocked so that the vehicle occupant is free to move about during normal operation of the vehicle. However, during sudden decelerations or changes in inertia, as during a crash, the retractors automatically lock to prevent further protraction of the safety belt webbing and to securely hold the vehicle occupants.
The normally unlocked retractor usually takes two different forms. The first form is belt sensitive and senses rapid movement of the passenger pulling on the belt. Upon sensing such rapid protraction of the belt from the reel, the retractor automatically locks preventing further safety belt protraction. A second form of automatic seat belt locking system is the inertia controlled system wherein the retractor automatically senses changes in the inertia of the vehicle and locks in response to sudden inertia changes. Retractors have also been developed which are both belt sensitive and vehicle sensitive and lock when either the vehicle undergoes a rapid change in inertia or the belt is protracted rapidly from a retractor reel.
The usual form for the retractor includes a frame with two upstanding sidewalls and a reel mounted between the upstanding sidewalls. Ratchet wheels are mounted on the ends of the reel and rotate with protraction and retraction of the safety belt. One or more locking bars are provided to engage the ratchet wheel. The locking bar is movable between an unlocked condition which allows free protraction of the safety belt from the reel and an emergency or locked position whereby the locking bar engages the ratchet wheels to prevent further protraction of the belt from the reel.
In order to maintain the maximum degree of safety, the locking bar must move rapidly between the unlocking condition and the emergency or locking condition. Any delay caused by friction or non-alignment of the locking bar in its mounting on the frame could cause a delay in the locking bar attaining its locked position with the ratchet wheel. Even a small delay may cause the belt to protract a sufficient distance so that it no longer holds the vehicle occupant as tightly as it should. If the occupant is not securely held, he may effect too much freedom of movement within the vehicle cabin during a crash and may be injured on the cabin interior.
In the prior art, the locking pawl normally has two ends extending through the frame. These ends lie generally in triangularly shaped holes and the locking pawl pivots at the apex of the triangle between the two adjacent sides. Usually the front of the triangle is an arch to accommodate the pivoting of the ends of the locking pawl. In order to assure unobstructed movement of the locking pawl from the unlocked position to the locked position, the triangularly shaped hole has had to be of close tolerances. Of course, any narrowing of tolerances increases manufacturing costs not only by increasing the cost of tooling and equipment necessary to meet the tolerances, but also in the cost of rejected parts which fail to meet more rigid specifications.
Not only is the size of the hole a crucial dimension, the lock pawl must fit between the spaced walls and must not be free to move about axially between the sidewalls. Only tabs extending from the side of the locking pawl extend through the triangular shaped holes and part of the lock bar extends adjacent to the inside of the sidewalls. Excess axial movement can cause the sides of the locking pawl to contact the inside of the sidewalls which would slow rotation of the locking pawl in an emergency and might prevent sufficiently rapid locking of the locking pawl.
Therefore, it is an object of the present invention to provide an improvement in a locking pawl mounting which will correct the problems associated with prior art devices. More specifically, it is an object of the present invention to provide a mounting for the locking pawl which will provide for ease of rotation between the locking pawl tabs and the axially aligned openings. A further object of the invention is to provide for smooth, non-interfering movement between the ends of the locking pawl and the sidewall. A further object of the invention is to provide a low-cost locking pawl mounting which eliminates the need for extremely strict tolerances in the retractor mounting. Still a further object of the invention is to provide a mounting which will remain reliable within increasing age and will not wear fast. A further object of the invention is the elimination of excess noise caused by movement of the locking pawl relative to the sidewalls and movement of the tabs of the locking pawl within the axially aligned holes of the sidewalls. Other objects will become evident in the foregoing description of the preferred embodiment of the invention.